SEC-2622: Set classesDirectory if exists for integrationTomcatRun
Fix jdbc-jc to work with tomcat gradle plugin

It is necessary to ensure that src/main/webapp exists to ensure the
application starts with the Tomcat Gradle Plugin.

This commit adds a Manifest file to src/main/webapp/META-INF to ensure
that git contains the otherwise empty directory.
SEC-2635: Add Geb integration tests for jdbc-jc